1. Field of the Invention
This invention relates to an improved mixture or blend of solid carbonaceous materials, and particularly to a blend of asphaltite with bituminous coals or lignite.
2. Prior Art
There is a material available in nature, usually obtainable by mining, which is known as asphaltite. This material is not classified as coal, although it has been referred to as "oil bearing coal." Asphaltite is instead solidified petroleum composed of 25-75% fixed carbon which resulted from the progressive loss of the volatile constituents contained in the bitumen. Grahamite which occurs in Pushmataha County, Okla., is a general type of asphaltite. It is characterized as having 30-55% fixed carbon; also, it is fusible and soluble in carbon disulfide. Solubility in carbon disulfide is the criterion that separates asphaltites from coals. Grahamite from the Pushmataha mines has been used for various purposes such as; manufacturing roofing, waterproofing compounds, candles, ointments, powders, beeswax, paints, varnishes, lining for chemicals tanks, roofing pitch, insulation for electric wires, garden hoses, binder for pitch in making coal briquettes, rubber substitutes, filler for brick and stone blocks, and molded insulation. The grahamite mined in Oklahoma and Arkansas is generally representative of similar low volatile coals such as albertite and impsonite found in Virginia, West Virginia and Pennsylvania.
At present however, asphaltite is not often used in coking processes because it burns too hot and burns out grates. This problem could be cured by utilizing water-cooled grates, but such equipment is expensive and is usually not installed merely to facilitate the burning of asphaltite. There are various other bituminous materials that have a certain heat content, but also have drawbacks that limit their use. For example, when North Dakota Lignite is ground up, the fines or dust below 28 mesh are removed. This material does not have a significant use unless the expensive process of pelletizing or agglomerating the fines is carried out. There are also eastern bituminous coals, for example, low volatile metallurgical coals, which are presently unsaleable because of their lack of volatile matter.
Lignite itself has a free swelling index (FSI) of 0, which means that it is substantially nonagglomerating and not useful at all for coke.